Electrophysiology is the study of electrical impulses that are transmitted through the heart and is focused primarily on diagnosing and treating arrhythmias, or conditions in which electrical impulses within the heart vary from the normal rate or rhythm of a heartbeat. A common arrhythmia is atrial fibrillation (AF), which is characterized by rapid, disorganized contractions of the heart's upper chambers, the atria. AF results from abnormal electrical impulses propagating through aberrant myocardial tissue pathways, which leads to ineffective pumping of the blood through the heart, as well as other complications. Atria flutter (AFL), another type of arrhythmia, is characterized by a rapid beating of the atria. Unlike AF, AFL arises from a single electrical wave that circulates rapidly throughout the right side of the heart. Since this arrhythmia can arise from multiple electrical sites, effective treatment of these conditions requires electrical isolation of the aberrant signal sites, thereby forcing the heart's normal conduction pathway to take over.
The practice of interventional electrophysiology for treating arrhythmias generally involves inserting catheters into a patient's vasculature (e.g., through the groin and inferior vena cava) and navigating the distal or “working” end of the catheters into the patient's heart chambers to identify or “map” the locations of heart tissue that are a source of the arrhythmias. The mapping of the heart's electrical activity is typically accomplished using one or more pairs of electrodes that are axially spaced apart from each other along the working end of the catheter. Following or in conjunction with the mapping procedure, the attending physician may use a separate ablation catheter or ablation electrode carried by the catheter that is also used for mapping to disable (or “ablate”) the tissue containing the aberrant signal(s) or signal pathway(s), thereby restoring the heart to its normal rhythm.
Electrical activity is normally mapped using much smaller electrodes (in surface area) than are used for performing ablation procedures. Because there is significantly less current transmitted through a mapping electrode circuit than through an ablation circuit, lead wires that connect mapping electrodes to processing circuitry (e.g., via a pin connector in the catheter handle) are much smaller than are used to couple ablation electrodes to an RF generator. As such, a larger number of electrodes may be provided on a mapping catheter than on an ablation catheter having a same or similar profile.
Examples and further aspects of known catheters are described in U.S. Pat. Nos. 4,739,768; 5,257,451; 5,273,535; 5,308,342; 5,984,907; and 6,485,455, the contents of which are incorporated herein by reference.